1. Field of the Invention
The present invention relates to a robot control system and more particularly, it relates to a robot control system which selects a suitable set of functions in accordance with a force, an acceleration, a velocity and a work rate. The robot control system according to the present invention can control an end effector and a manipulator of a robot for a suitable operation based on a control signal from a control means which is provided in correspondence with a selective function device. The work rate is given by a product of speed and force.
2. Description of the Related Art
In general, a robot is formed of an end effector (or, hand) provided at the end of an arm (a manipulator) to grasp/push an object, a plurality of sensors mounted at the end effector for detecting a force, a position, and an orientation of the end effector, and a control unit for controlling the operation of the manipulator.
There are three different control methods well-known in the conventional art, i.e., a force control method, a position control method, and a stiffness/dumping control method, in accordance with the relationship between the end effector and the object. That is, these methods are distinguished in accordance with the following states, i.e., first, a contacting state (or, non-contacting state) between the end effector and the object, second, characteristics of the object (i.e., rigid or non-rigid body), and third, the state of the object (i.e., fixed or not fixed).
Concretely, the force control method is used for a contacting state between the end effector and a fixed and rigid object. The position control method is used for a non-contacting state between the end effector and an object. The stiffness/dumping control method is used for a contacting state between the end effector and a not fixed or non-rigid object.
Furthermore, the force control method and the position control method can be combined with each other, and this combination is called a hybrid position/force control method. Also, the position control method and the stiffness/dumping control method can be combined with each other, and this combination is called an impedance control method.
As is obvious from the above, the hybrid control method is only used for contacting or non-contacting state between the end effector and the fixed and rigid object, and the impedance control method is only used for contacting or non-contacting state between the end effector and the not fixed or non-rigid object.
However, there is no general method which is able to cover both of these two methods in the conventional art.